1. Field of the Invention
This invention relates to a data processing apparatus in which a CRT (Cathode Ray Tube) and an impact printer are integrally and preferably arranged on a chassis.
2. Description of Prior Art
In a data processing apparatus, a CRT display and a thermal printer (non-impact printer) are mounted integrally on a chassis and covered by a cover plate. Within a limited space area, it is rather difficult to house these units as one unit compactly without adversely affecting printing quality. There are still some other apparatuses which divide the body case into several parts as compartments and encase these units respectively in compartments to allow highly efficient printing performance whereby printing is conducted without being adversely affected by external factors such as mechanical vibration during printing.
Concerning these kinds of data processing apparatuses, the CRT screen is vertically set and the thermal printer is set on the upper backside of CRT display. This type of data processing apparatus has not shows any failure in printing operation and quality but causes problems when the printer is replaced with a typewheel printer in machines equipped with the thermal printer and CRT display.
This trouble is attributable mainly to a fragile chassis construction which is not rigid enough to withstand the total working weight of printer while it is in printing operation, thus resulting in deteriorated printing quality. The images displayed on the CRT screen are also deflected and chattered. As long as this kind of conventional data processing apparatus is used, a small scale printer such as thermal printer, is not a problem even if it is arranged at the upper backside of a CRT display.
However, when a typewheel printer ( as disclosed in U.S. Pat. No. 4,049,109) is employed, the typewheel having a plurality of characters on the outer periphery must be upright on a bottom side of a housing so that characters to be printed on a printing sheet on a platen can be seen. In order to strike the typewheel which is vertically arranged to the bottom of the housing, a ribbon cassette and a printing hammer must be vertically arranged against the typewheel.
Therefore, as shown in Japanese Utility Model Disclosure NO. 60-8041, the housing becomes taller than a diameter of the typewheel causing difficulty in stacking and transporting the data processing apparatus. In orer to reduce a height of the housing, a setting angle fixing the typewheel to the bottom side of the housing is contrived; however, a relative location of the printing hammer and the ribbon cassette must also be contrived.
Moreover, printed characters on the sheet cannot be seen behind the typewheel and the printing when set at such an angle. Also when the typewheel printer is provided with means for driving the typewheel and the printing hammer, it is much taller and longer than the thermal printer and extension of the total size of the data processing apparatus is limited. Accordingly, the problems associated with conventional data processing apparatus become very large scale when it is provided with typewheel printer at the upper rear part of CRT display as the images displayed on the CRT display are also swayed by the leakage from magnetic flux of the typewheel printer.